Conventionally, physical quantity sensor devices capable of detecting a physical quantity (e.g., an angular velocity, an acceleration, etc.) are used in a variety of technical fields such as detection of a shake of a digital camera, attitude control of a mobile unit (e.g., an aircraft, an automobile, a vessel, a robot, etc.), and guidance of a missile and a spacecraft. In general, a physical quantity sensor device includes a physical quantity sensor that outputs a sensor signal in response to a physical quantity given externally and a physical quantity detection circuit that detects the physical quantity sensed by the physical quantity sensor based on the sensor signal supplied from the physical quantity sensor.
In recent years, with the progress of the circuit nanotechnology, digitalization of the physical quantity detection circuit is on its way to further advance. Patent Document 1 discloses a signal processing circuit for a biaxial angular velocity/acceleration sensor, which is composed of digital circuits. In this signal processing circuit, while an analog-to-digital converter circuit converts a sensor signal from the sensor to a digital sensor signal, a sine wave signal generation circuit generates a digital sine wave signal, and a digital multiplier circuit multiplies the digital sensor signal by the digital sine wave signal, to thereby obtain a digital physical quantity signal corresponding to the physical quantity sensed by the physical quantity sensor. Patent Document 2 discloses a capacitive sensor device, in which an analog sensor signal is under-sampled with a sampling frequency that is 1/n (n is an integer) of the carrier frequency of the analog sensor signal, and then subjected to analog-to-digital conversion, to obtain a digital physical quantity signal.    Patent Document 1: Japanese Patent Gazette No. 2728300    Patent Document 2: Japanese Translation of PCT International Application No. 2004-526942